I'm currently in the process of building a fridge, i'm not an electrician but the STC-1000 is really easy to wire, if you can wire up a plug then you should be able to follow the simple wiring diagram, breaking down the costs though, STC-1000 was ã9, project box ã5, (you dont need to spend a fortune on the box, some people use a plastic ice cream tub which costs nothing) couple of plug sockets, ã2 (B&Q Cheapo's) wire and connectors i have, so for the controller i'm into ã16 so far.
I'm adding extra bits (which you don't really have to) water proof in and out glands and an extra plug socket coming directly from the mains in feed, this way i can plug in a 12v fan or another device at a later date if i want to - runs up my controller costs a few quid though.
The fridge itself cost me ã25 on fleabay - top tip if you want a mega cheap fridge, go down the local council dump and see if they have any, (someone told me this after)
Theres a bit of faffing about making a table / platform at the bottom, i used old of cuts of wood and even painted it white so it looks nice
you'll need a heater, i used a 60W green house heater which cost me ã12 again on fleabay - I've wired in a longer length of wire (which again was really easy) as the lead it came with was really short, and it didn't come with a plug, so had to add that to.
My top tips, and if i did it again - i'd buy a larder fridge, mines an under counter fridge, it works but the FV just fits, i'll have to mix and cast the yeast, then lift it into the fridge, it would have been nice to mix in situ and have additional storage space above the FV, and if next time maybe a bit deeper fridge, i've had to cut the shelf guides of the inside of the door so it will shut - again no big deal but just more faffing about.